In the overnight to early morning hours on Thursday, 1 February 2018, Volcan de Fuego in Guatemala awoke and produced a rather impressive ash plume that was easily observable in GOES-16 (east) imagery. The eruption started around 0200 UTC and ended around 2200 UTC, with the majority of ash occurring from ~0900 UTC to 1800 UTC. The Washington Volcanic Ash Advisory Center (VAAC) located at the NESDIS Satellite Analysis Branch (SAB) has access to various satellite channels and products, including the Ash, Dust, and SO2 RGB products. Questions have arisen over the years on the most appropriate times to use these products (no two eruptions are alike) and this particular eruption provided the analysts the opportunity to evaluate each RGB against the visible and infrared channels.

Jamie Kibler (Ops and VAAC Manager) provided some valuable insight on how each channel or products behaved, so the remainder of this blog post will be his critique.

GOES-16 GeoColor animation of the Volcan de Fuego Eruption on 02/01/18. Click here to enlarge.

“Channel 2 VIS (substituted the GeoColor product for this animation) – did well picking up the ash, but the real thin ash moving northerly from the summit – due to clouds could not really see it after a couple of hours. But everything else looked good.” Note: Also notice the cooling signature (light blue coloring moving slowly over the water) south of Mexico due to the gap winds (Tehuano wind) over the Gulf of Tehuantepec.

“RGB Ash – Did a very nice job picking up ash in all directions and could track it well, but as it got more thin over time (19z-23z) could not really see it very well……too pixelated and not very bright (possibly due to limited colors in N-AWIPS)”

“Dust and SO2 RGBs – did a really good job detecting the ash and even as it thinned it still did a good job in detecting the Ash/SO2 – the winner of all the channels/rgbs. Both just showed up much brighter than Ash RGB”

Due to the extent of the ash plume, SAB called for a Mesoscale Domain Sector (MDS) to be place over Central America from ~2045 UTC on 01 February 2018 to ~1200 UTC on 02 February 2018. The 0.64 𝞵m visible animation above shows the ash drifting west over the nearshore waters of Guatemala. This was the first official MDS request by the Washington VAAC!

I’d like to thank Jamie for contributing on this very interesting event!

The tropical Atlantic has been putting on quite the show over the last couple of weeks of Hurricane Harvey (Category 4). . .I’m sure you heard of that one, followed by Irma (Category 5), Jose (Category 4), and Katia (Category 2). Katia made landfall last night in Mexico and now we continue our focus on Irma and Jose. Why is it so active? A few reasons: warm ocean (sea surface temperature and high ocean heat content), lack of a true El Nino Southern Oscillation (ENSO) signal, though it looks like a weak La Nina, little to no shear throughout much of the basin, a lack of dust from the Sahara, and a strong Azores high. Oh yeah, on top of that, we have the Madden-Julian Oscillation (MJO) more or less stuck in favorable phases for the Atlantic (8, 1, 2, 3) and forecasts suggest that stays in place for a while.

ECMWF MJO verification and forecast courtesy of the Climate Prediction Center (CPC). Click here to open in a new window.

GEFS MJO verification and forecast courtesy of CPC. Click here to open in a new window.

One product I noticed in use at the Ocean Prediction Center (OPC) on Friday, 09/08/17 was the GOES-16 Daytime Convection RGB, so I thought this would be a nice opportunity to show you all three current Atlantic systems with a comparison to the 10.3 µm “clean” channel.

GOES-16 Daytime Convection RGB of Hurricane Irma valid 1100 UTC to 2300 UTC on 09/08/17. *Preliminary, Non-Operational Data* Click here to open in a new window.

Note the bright yellow coloring that highlights, new convection with smaller ice particles indicating strong overshooting tops in the outer rainbands, while the main central dense overcast (CDO) surrounding the eye also gets brighter. This indicates that after the eyewall replacement cycle ended, the new eyewall started to contract and strengthen (winds at this time were 155 mph, but shortly after this strengthened to 160 mph.

GOES-16 10.3 um “clean” infrared window channel similar to the previous animation of Hurricane Irma. *Preliminary, Non-Operational Data* Click here to open in a new window.

Notice that the 10.3 µm “clean” window shows us the brightness temperature of the coldest cloud tops. Although you can see the new overshooting tops, as those thunderstorms rotate around the CDO, it gets more difficult to identify the newer, important convection.

GOES-16 Daytime Convection RGB for Hurricane Jose valid 1000 UTC to 2045 UTC on 09/08/17. *Preliminary, Non-Operational Data* Click here to open in a new window.

By contrast, notice how compact Hurricane Jose became as it strengthened to a 150 mph Category 4 hurricane on Friday (09/08/17). Again, the beginning of the animation shows plenty of yellows that indicate new convection, wile the older convection fades to oranges, then reds. Also notice how the CDO becomes more yellow as the eye becomes cleaner and the storm takes on a more donut structure, even with the strong outflow channel to the northeast that makes the storm look lopsided. Could this RGB be helpful in identifying CDO changes? Or help with indicating eyewall replacement cycles (ERCs) in conjunction with microwave imagery?

GOES-16 10.3 um “clean” infrared imagery similar to the previous animation of Hurricane Jose. *Preliminary, Non-Operational Data* Click here to open in a new window.

Again, to contrast the Daytime Convection RGB, the above 10.3 µm animation shows very cold cloud tops, but the newer convection starts to blend in with the CDO over time. Do you see other differences?

GOES-16 Daytime Convection RGB of Hurricane Katia valid 1200 UTC to 2357 UTC on 09/08/17. *Preliminary, Non-Operational Data* Click here to open in a new window.

Finally, Hurricane Katia was very small in comparison with the other two hurricanes, but notice there are differences in the intensity of the convection on Friday (09/08/17). What do you see in the imagery? There are less yellows than in Irma or Jose, yet the storm intensified to a Category 2, 90 kt (105 mph) hurricane prior to landfall on Friday evening. The warming clouds and less cold, newer convection may have been due to dry air entrainment due to the close proximity to mountainous land nearby and a weak trough to the north.

GOES-16 10.3 um “clean” infrared imagery similar to the previous animation of Hurricane Katia. *Preliminary, Non-Operational Data* Click here to open in a new window.

How does the 10.3 µm imagery above contrast with the Daytime Convection RGB?

So, what is steering Irma? What about Jose and Katia? Well, I’m glad you asked. . .

GOES-16 Air Mass RGB image valid at 0900 UTC 09/09/17. *Preliminary, Non-Operational Data* Click here to open in a new window.

The GOES-16 Air Mass RGB image (courtesy of NASA SPoRT) above with my crude drawings show a rough idea of the players affecting the steering flow around the three hurricanes. Katia has made landfall as it was pushed southwest due to the old cold frontal boundary (responsible for the cool air in most of the country) along with a disturbance highlighted in the yellow circle. This disturbance will close off over the Tennessee Valley area and help to pull Hurricane Irma north, then northwestward in the next 48 hours. Finally, Jose (east of the Lesser Antilles) will be pulled north through a weakness in the ridge due a weakness created by the Tropical Upper Tropospheric Trough (TUTT in the yellow “T”) to the northeast and Irma’s broad circulation. Since the current trough over the northeast U.S. moves east/northeast and the central Atlantic TUTT remains stationary, Irma gets left behind in the southeast U.S., but weakening after landfall, while Jose gets left behind and may perform a tight anticyclonic loop before “possibly” moving northwest. We’ll deal with Jose later. . .

I have included the GOES-16 Air Mass RGB and 7.3 µm low-level water vapor animations below so you can get a better feel of the overall pattern.

On 15 June 2017, the Storm Prediction Center had a Moderate Risk for Severe weather (for wind) out for much of the southeast half of Kansas, with a enhanced risk area (for hail) extending southwest into the Texas Panhandle. Morning GOES-16 split window difference imagery showed low-level moisture boundaries/moisture pooling setting up across the region. The relatively light shades of gray indicate regions of relatively high low-level moisture content. Of particular note is a w-e strip of ll moisture across western Kansas and another sw-ne oriented gradient extending from the Texas Panhandle into southern Kansas. By the end of the morning, cu could be seen developing within these areas. See this blog post for details on the split window difference.

The AWIPS Tracking Meteogram Tool provides forecasters with a means of graphing trends in a field. In this case, one can quantify and visualize how rapidly cloud top temperatures cooled with this storm. The developing thunderstorm cooled a remarkable 70C from 1727 UTC to 1827 UTC (10C to -60C) (Figure 3).

Several GOES-16 derived products recently became available to NWS forecasters in AWIPS. GOES-16 CAPE and PW showed increasing values through the day prior to initiation. Storms in Kansas developed within a local TPW and CAPE max, while storms in Texas developed along a sharp gradient (Fig 4 and 5). The GOES-R TPW and Derived Stability Indices algorithms have been tested in the HWT using legacy GOES Sounder data as a proxy. Evaluations showed that the GOES-derived indices depict the location and movement of boundaries and local min/max well. More feedback on these products can be found on the GOES-R HWT blog here.

“The GOES-16 data posted on this page are preliminary, non-operational data and are undergoing testing. Users bear all responsibility for inspecting the data prior to use and for the manner in which the data are utilized.”

On the morning early of 04/06/17, TAFB forecasters noted a nice V-pattern to convection at the tail end of a front in the northeast Gulf of Mexico. The increased temporal and spatial resolution of GOES-16 compared to the GOES-13 (east) provided more details on the organization and maintenance of the convective line that would otherwise have been analyzed.

Hugh Cobb (TAFB Branch Chief) noted: “We also looked at the Red VIS Band 2 for this event. The VIS imagery was more striking in that you could see the shadows of the high cirrus cast on the lower cloud deck in the animation and the “beavertail” of of the low clouds feeding into and maintaining the deep convection.”

Jorge Aguirre-Echevarria (TAFB Forecaster) noted that “the striking cloud/convective signature and associate lightning activity observed that day over the waters of the far southern Gulf of Mexico.” In particular, these events are rather rare at such a low latitude in the TAFB Offshore Zones. The GOES-16 10.3 μm infrared imagery proved to be very helpful in seeing the overshooting tops and the cold cloud canopy temperatures which signified the activity would persist west of Key West, FL.

Strong thunderstorms erupted on the evening of 04/28/17 and continued into the overnight, expanding in coverage and producing prolific lightning in spots. The Weather Prediction Center’s Metwatch Desk was particularly busy issuing multiple Mesoscale Precipitation Discussions (MPD) to stay ahead of the flash flood threat.

“GOES-16/EAST WV LOOP SHOWS A RELATIVELY FLATSHORTWAVE ACROSS NW OH WITH THE TRAILING TROF SW ACROSS CENTRALIND/IL WITH A MCS TRACKING ACROSS CENTRAL IND. THIS MCS IS AT THEAPEX OF SOUTHWESTERLY LOW LEVEL JET/WAA REGIME OVERRUNNING A WARMFRONT THAT EXTENDS FROM LWV…N OF LOU AND S OF CVG. THIS COMPLEXHAS BEEN PRODUCING 1.5-2.5″ RAIN AS IT TRACKED THROUGH WESTCENTRAL IND…AND WILL LIKELY MAINTAIN AS IT CROSSES INTO LOWERFFG VALUES ACROSS SE IND/SW OH IN THE NEXT HOUR OR SO.”

As Greg mentioned, GOES-16 6.9 μm “mid-level” water vapor imagery shows a relatively flat shortwave aiding in the maintenance of the Mesoscale Convective System (MCS) over Indiana and Ohio, while a stronger shortwave can be seen moving out of Iowa into southeastern Minnesota. What other features can you identify in this animation?

The GOES-16 1-minute 0.64 μm “Red” visible animation shows the incredible detail in the cloud top environment (0.5 km resolution) of the aforementioned MCS moving through Indiana and Ohio. Note the persistent overshooting tops and their subsequent gravity waves rippling across the cirrus shield. This is indicative of healthy, organized updrafts which a forecaster can then make a decision on whether the activity will persist, strength, or weaken with time.

Once again, the 1-minute imagery proves valuable here as the trend of the cold cloud tops can be seen expanding with the MCS, while new convection fires near the Illinois, Kentucky, and Indiana borders. Note the dark pixels indicating very cold overshooting tops. Can you spot the enhanced-V structures down-stream from those towers?

The ongoing MCS in the above GOES-16 10.3 μm “Clean” infrared animation with GLD-360 5-minute lightning density overlaid appears to weaken a bit as new convection farther southwest takes advantage of a stout low-level jet. Notice how the lightning cores are exceeding the color scale that was set by the developers at OPC and NESDIS. Grant it, the color scales are somewhat limited by the GEMPAK software (6.5 bit or 96 colors), yet it’s safe to assume the lightning activity is very intense.

Finally, around 0500 UTC on 04/29/17, Andrew Orrison again referenced GOES-16 in his analysis of the well-defined (new) MCS which developed overnight:

“THE SATELLITE PRESENTATION OF THE CONVECTION IS VERY IMPRESSIVEWITH THE EXPERIMENTAL GOES-16 10.3 MICRON/IR IMAGERY DEPICTING AVERY LARGE AREA OF VERY COLD CONVECTIVE CLOUD TOPS…REACHINGNEARLY -80C…WITH NUMEROUS OVERSHOOTING TOPS EMBEDDED WITHIN THECONVECTIVE MASS. THIS IS INDICATIVE OF VERY STRONG FORCING WHICHIS ENHANCED NOT ONLY IN THE LOW LEVELS GIVEN THE LOW LEVEL JET ANDISENTROPIC ASCENT…BUT ALSO BROADLY DIFFLUENT FLOW ALOFTASSOCIATED WITH RIGHT-ENTRANCE REGION JET DYNAMICS.”

As Andrew referenced in his MPD, as the night progressed, the convection along the Midwest through Ohio Valley erupted into an elongated MCS with embedded Mesoscale Convective Vortices (MCVs) that will have to be watched later in the day.

WPC Day 1-3 QPF issued at 2040 UTC on 04/28/17 and valid from 0000 UTC 04/29/17 to 0000 UTC 05/02/17. Click to enlarge

As you can see in the above Quantitative Precipitation Forecasts for Day 1 (top) and Days 1-3 (bottom), this was only the beginning of a prolonged flood threat for the Mid-Mississippi Valley and eventually farther north to western Michigan.

GOES-16 is certainly proving to be useful in operations as the increased temporal and spatial resolutions when compared to GOES-E (13) and GOES-W (15), provides more detail, fluidity, and trend monitoring to assist in the forecast decision-making process. Additional channels, multispectral imagery (RGBs), band-differences, and derived products will be explored throughout 2017, so please stay tuned for more posts!

One of the fascinating aspects of GOES-16 is how much better the resolution is at higher latitudes, near the limb or edge of the footprint. Forecasters at the Ocean Prediction Center (OPC) noted how much easier it is to see the ice sheet (when clouds allow) and even the breaking up of this ice into groups of icebergs!

The 0.86 µm near-infrared “Veggie” channel animation above shows the ice swirling or drifting near Labrador and New Foundland. The 1-km resolution imagery is more resolved around 2 km at this latitude due to the, yet you can see amazing detail in the ice breaking up and moving around. Note: The imagery jump is due to GOES-16 ongoing testing during the beta period.

Aqua MODIS 0.86 um “Veggie” image of the ice “swirls” off the Labrador coast valid on 04/24/17. Click to enlarge

The Aqua MODIS image above shows a more nadir view of the ice swirls east of Labrador on 04/24/17. This image is higher resolution (1 km) than the GOES-16 animation above and provides great details that were not previously available to OPC forecasters.

The Iceberg Analysis from 04/24/17, shows the extent and number of icebergs that are being tracked this spring. According to this CBC News article, “about 450 icebergs near the Grand Banks of Newfoundland, up from 37 a week earlier, according to the U.S. Coast Guard’s International Ice Patrol in New London, Connecticut. Those kinds of numbers are usually not seen until late May or early June. The average for this time of year is about 80.” More than 600 icebergs have been spotted in shipping lanes that made the Titanic unfortunately, famous. A couple photos are included below.

This morning there were a lot of contrails evident on the GOES-16 data. Looking at the VEF 12Z 10 APR 2017 sounding (see below), conditions look good for them – lots of high-level moisture. From this, we expect most of the contrails to be in the 200-300 mb (which is around a cruising altitude of ~30,000 ft).

Of course we can’t see the contrails until the sun comes up in the visible and near-IR bands. However, using the different water vapor bands, we can still see them (the improved resolution helps too!). Using this website to learn about weighting functions, we can get a general idea of the level at which the weighting function for each water vapor channel peaks. Since contrails are typically located high in the troposphere, they will appear similarly visible in all three water vapor channels. In other words, most water vapor absorption for the three water vapor channels (see weighting functions below) takes place below the level at which a typical contrail will be located. The 7.34 um channel will be slightly better than the other two water vapor channels at detecting upper level cloud features such as contrails since it is the least sensitive to water vapor absorption.

Once the sun does come up, we can use our other bands. In this loop, I have the Red Band (Ch 2, 0.64 um) in the top-left, the Cirrus Band (Ch 4, 1.38 um) in the top-right, and the Snow/Ice Band (Ch 5, 1.61 um) in the bottom-right. First thing I notice is that the contrails don’t show up the best in the Red Band, the Cirrus band pops them the best. According to the GOES-R ABI Fact Sheet for the Cirrus Band,

The “cirrus” near-infrared band at 1.37 μm will detect very thin cirrus clouds during the day. This band is centered in a strong water vapor absorption spectral region. It does not routinely sense the lower troposphere, where there is substantial water vapor, and thus provides excellent daytime sensitivity to high, very thin cirrus under most circumstances, especially in warm, moist atmospheres.

Thus the high-clouds pop against a muted background of the lower troposphere. If you watch this loop, you can also see the contrails increase in abundance as we progress from 12Z through 1530Z. That is due to the increase in air traffice, which is confirmed with this loop (from Planefinder.net).

“The GOES-16 data posted on this page are preliminary, non-operational data and are undergoing testing. Users bear all responsibility for inspecting the data prior to use and for the manner in which the data are utilized.”